Developmental age trends in crossing the body midline in normal children.

The ability to cross the body midline was assessed in 150 normal children, ages 4 through 8, by observing hand usage during the Space Visualizaion Test of the Southern California Sensory Integration Tests. A Space Visualization Contralateral Use score (SVCU) was computed for each subject and was regarded as a measure of the tendency to spontaneously cross the body midline. This score is based on a ratio of ipsilateral (uncrossed) to contralateral (crossed) responses. The percentage of time a child use the preferred hand to pick up a block was also recorded. Results indicated that spontaneous midline crossing increased with age. Although the percent of preferred hand responses increased with age, there was enough variability at each age that there were no significant differences among age groups. Perceptual, motor, and psychosocial factors that could influence midline behavior were discussed. Based on the data from this study, a preliminary reinterpretaton of the SVCU score is offered.